It is not an overstatement that the entire world runs on human relationships  - implicit contracts, accepted social behavior, quid pro quo, and yes, corruptions. We do things for family member that we would not do for strangers because family members have done the same thing for us in the past, Parents and children feel obligation to each other. Friendship also means an implicit understanding of helping each other in times of need as well as reciprocal favors such as dinner invitations and gift giving. Quid-pro-quo is a loosely understood social norm, but NOT an implied contract between otherwise strangers over specific and explicitly related acts of exchange. That is CORRUPTION - paying bribes to people to do legal or illegal acts they otherwise will not do for unrelated or related people. While the distinction between these acts of human relationship are understood easily and operate rather smoothly to enable our civilization to work,  the defining boundaries between normal social realtionship,.favors, and corruption are not always clearly defined and remains fuzzy which is the reason for lawsuits and endless disputes. But that is what makes life interesting as well as complex. Endless history, books, and novels have been written and will continue to be written about these human relationships, noble as well as failings. That is LIFE!